The present disclosure relates to wafer-level cameras, spacer wafers for wafer-level cameras and methods of manufacturing spacer wafers for wafer-level cameras, and, more particularly, to spacer wafers and methods for manufacturing spacer wafers using photolithographic and microfabrication techniques.
In wafer-level cameras, spacer wafers are typically aligned with a solid substrate, such as a glass wafer, and bonded to the solid substrate using an epoxy. This is commonly done before lenses are fabricated on the solid wafer. This spacer-to-wafer bonding is difficult, since epoxy must be applied between the spacer wafer and the solid wafer, but not in or over any spacer holes. Also, an uneven bond thickness can result in variable spacer thickness.
Conventional spacer wafers for wafer-level cameras can commonly be formed of glass wafers. Spacer wafers are commonly manufactured by drilling holes through the glass wafers. The drilling process is typically carried out by laser cutting, although abrasive water jet cutting, sandblasting, chemical etching or other processes are also possible. Laser drilling is extremely expensive and time consuming. For example, it is not uncommon for 80 percent of the total manufacturing cost of a spacer wafer for a wafer-level camera to be in laser drilling. Laser drilling also involves long lead times. If a new array pitch or hole diameter is required, it may take weeks or longer to procure a spacer. This is especially prohibitive in rapid prototyping of lens designs and development work. Also, in conventional approaches, the possible spacer thicknesses are limited to the available standard glass wafer thicknesses.